Frequency modulated video film recording



Feb. 1, 1966 J. T. MULLIN 3,233,039

FREQUENCY MODULATED VIDEO FILM RECORDING Original Filed Deo'. 9. 1960 3Sheets-Sheet 1 Feb. 1, 1966 J. T. MULLIN 3,233,039

FREQUENCY MODULATED VIDEO FILM RECORDING Feb. l, 1966 J. T. MULLIN3,233,039

FREQUENCY MODULATED VIDEO FILM RECORDING Original Filed Deo. 9, 1960 3Sheets-Sheet 5 United States Patent O 3,233,039 FREQUENCY MODULATEDVIDEO FILM RECORDING John T. Mullin, Beverly Hills, Calif., assignor toMinne- Sota Mining and Manufacturing Company, St. Paul, Minn., acorporation of Delaware Original application Dec. 9, 1960, Ser. No.75,464.

Divided and this application Sept. 29, 1964, Ser.

Claims. (Cl. 178-6.7)

This invention relates to recording and reproducing systems and, moreparticularly, to such systems capable of recording and reproducingsignals over a wide frequency range such as, for example, video signals.

This application is a division of Patent No. 3,137,768, formerly SerialNo. 75,464, filed December 9, 1960 entitled Transducing System.

Conventional apparatus for recording video information includes eithermagnetic tape equipment or photographic equipment. At first,photographic equipment was utilized even though it had manydisadvantages because the tape equipment Was limited at reasonable tapespeeds with respect to its usable frequency range. The video image wasrecorded as successive frames in accordance with conventional motionfilm techniques. Magnetic tape recording equipment has, however, beendeveloped for transversely recording and reproducing signals covering arelatively wide frequency range across a magnetic tape. This transverserecording equipment is in the main equipment currently utilized forrecording video information.

One such transverse recording equipment utilizes a rotary magnetic headassembly provided with magnetic units arranged to sweep successivelyacross a relatively wide magnetic tape. While such equipment isworkable, it is subject to a number of important disadvantages. Forexample, while a fineness of detail can be recorded and reprod-uced inthe direction of the rotation of the high speed magnetic heads, detailin the direction of motion of the tape is very poor. The detail is poorbecause of the finite width of the head structure and because thesuccessive transverse tracks must be separated by a few thousandths ofan inch to avoid crosstalk between tracks. Another disadvantage is `thatthe high speed rotating heads must be very accurately controlled by highgrade servo systems to maintain synchronization and low flutter. Furtherediting of the tape is difficult because the operator cannot view thepicture by inspecting the surface of the tape. Still another importantdisadvantage is that the sound accompanying the video image is linearlydisplaced from. the recorded video information and not synchronized withthe transverse tracks. This latter disadvantage further complicates theprocedure of editing.

In a specific illustrative embodiment of this invention, thesedisadvantages are overcome utilizing a transverse recording andreproducing system capable of handling high grade picture informationaccompanied by high fidelity sound. In the specific illustrativeembodiment, high speed mechanical devices are not utilized and insteadhigh speed electronic devices are provided, such as cathode ray tubesand flying spot scanners. The recording apparatus may incl-nde twocathode ray tubes: a cathode ray tube for recording the video signals,and a cathode ray tube for recording the audio signals. The two cathoderay tubes are both associated with a strip of continuously moving filmwhich may function as the recording medium.

The video signals to be recorded may be of the type conventional in theUnited States comprising a succession of horizontal line scans. Thevideo signals are frequency modulated on a carrier and the modulatedcarrier is first rectangularized and then introduced to the cathode raytube for recording. Vertical defiection is not required 3,233,039Patented Feb. 1, 1966 because of the continuous movement of the fihnstrip adjacent the two cathode ray tubes. Gamma and gray scale problemsusually associated with film are non-existent because there are only twostates of the cathode ray tube current, on and off. Only two states ofcurrent are provided because the modulated carrier is rectangularizedbefore it is introduced to the video cathode ray tube. A typicalrecorded line of the video information, on examination under amicroscope, consists of a series of alternate dark and light dashes, theduration of which changes with the video information.

Features of this invention pertain to means for providing visible imagesat the film which is readily viewable by an observer. The images aresubstantially the same as the successive images represented by the inputvideo signals. The frequency modulation of the video signals is suchthat the lighter portions of the images represented by the video signalsprovide for lower frequencies and the darker portions for higherfrequencies. The successive lines on the film are recorded quite closetogether and the observer can view and edit the recorded picture quitereadily by providing light atan angle to the grating formed by thealternate dark and light dashes of the lines. The resultant interferencepattern provides for an image where the closely spaced dots in each lineblend together. Since these spots represent the dark portions of theoriginal image represented by the video signals, a picture lofsubstantially the same as the original image is provided to theobserver.

Further features of this invention relate to the provision of means forrecording the sound information accompanying the video information indirect line -by line synchronization with the transverse lines recordedacross the moving film. The audio cathode ray tube, mentioned above, isutilized for transversely recording the sound, and is driven insynchronization with the cathode ray tube for the video signals. Meansare provided for sampling the audio signals and for converting the audiosignals to pulse duration signals. The pulse duration signals aretransversely recorded across part of the film strip and the videomodulated carrier is recorded across another part of the film strip.Effectively, a recorded line extending across the film strip includestwo parts: a first part for the soundinformation which is recorded bythe audio cathode ray tube, and a second part for the video informationwhich is recorded by the video cathode ray tube. The duration of thepulses derived from the sound information determines the length of arecorded line in the first part for each of the transverse lines acrossthe film strip. The successive lines for the sound information on thefilm strip would appear upon a casual inspection to form a variable areasound track.

The maximum frequency of the sound recordable in this manner is limitedby the repetition rate of the transverse lines across the film striputilized to record the successive pulse duration signals. The samplingrate of the audio signals, however, may be increased by a predeterminedratio and a number of successive sound lines or group of such lines may-be recorded across the audio part of the film strip for each video lineacross the video pa-rt of the film strip. The first of each group ofsound lines may be initiated simultaneously with the video line so as tobe directly in line with the video line. High fidelity sound informationmay, accordingly be recorded which is in direct synchronization, line byline, with the video transverse line recording.

A pair of flying spot scanners may -be utilized for reproducing thevideo and sound information recorded on a film strip. Separate photocellmeans are positioned relative to the lm strip for receiving respectivelythe video and the audio -or sound information illuminated by the pair offlying spot scanners. Thus, line by line, the video signals a-rereproduced at the video photocell means aS one spot sweeps across thefilm, and at the same time the sound, in the form of varia-ble pulsesignals, is developed at the audio photocell means as the `other spotsweeps across the film. Means are provided for converting the pulseduration pulses to .amplitude modulation pulses and for integrating theamplitude modulated pulses to provide a varying signal which is the sameas the original audio signal provided for recording.

Further features of this invention pertain to the provision of noisereduction means for avoiding noise due to the presence of dirt on thefilm strip. Means are provided for controlling the flying spot scannerfor the audio signals to initiate each trace or line scan at an opaqueportion on the film strip. Each pulse on the film strip may be opaque ordark, and the trace starts just after the beginning of the recordedpulse. A pulse is developed by the associated photocell means at a timeposition when the scanning spot reaches the transparent portion of thefilm following the recorded pulse. Dirt either on the opaque recordedpulse or on the transparent portion following the pulse does not affectthe accuracy of the reproduction or introduce any noise.

Further advantages and features of this invention will become apparentupon consideration of the following description when read in conjunctionwith drawing where- FIGURE 1 is a functional representation of therecording apparatus of the recording and reproducing system of thisinvention;

FIGURE 2 is a functional representation of the reproducingr apparatus ofthe recording and reproducing system of this invention;

FIGURE 3 is a fragmentary View of the lm strip utilized in the recordingand reproducing system of this invention illustrating the dispositionandsynchronization of the recorded sound and video signals;

FIGURE 4 is a diagramattic yrepresentation of apparatus for viewing thesuccessively recorded images on the film strip; and

FIGURE 5 is a pictorial View of the apparatus for viewing thesuccessively recorded images on the film strip.

Referring first to FIGURE 1, which shows the reproducing apparatus ofthis invention, the signals to be `recorded may be conventional videosignals provided by a videol input `circuit 10, and high fidelity audiosignals accompanying the video signalswhich are provided from an :audioinput cricuit 36. The conventional television signal in the UnitedStates includes 525 horizontal lines at a repetition rate of 15,750lines per second for each frame. The repetition rate of the frames is 30frames per second, with each frame representing a separate image orscene. The video signals may also include horizontal and verticalsynchronization and blanking pulses.

The video signals are introduced from the circuit to` a frequencymodulator 11 for frequency modulating a carrier. The carrier may have :afrequency of approximately 5 megacycles which is suitable for modulationby the wide band television signals. The modulation is such that thevideo signals representing lighter portions of the images or scenesprovide for lower frequencies, and the darker portions provide forhigher frequencies. As is hereinafter described, this directionof'modulation is an important feature in the apparatus for viewing andediting the recorded frames. The frequency modulated signal from themodulator 11 is introduced to a circuit 17 which rectangularizes theindividual pulses of the frequency modulated carrier. Illustratively,the circuit17 may be a Schmidt trigger circuit which operates in onedirection when the carrier increases to a predetermined value and whichoperates in the other direction when the carrier decreases to apredetermined value.

The circuit 17 may also be an over-driven amplifier whichrectangularizes the frequency modulated signal. The output of thecircuit 17, accordingly, is a series of rectangular or fiat top pulseshaving a duration which varies in accordance with the video signals fromthe input circuit 10.

The rectangularized frequency modulated carried from the circuit 1'? isintroduced to the grid 13 of a video cathode ray tube 12. The cathoderay tube 12 is one of two cathode ray tubes 12 and 25 utilized in the'recording apparatus of this invention. The tube 12 is utilized torecord the video signals and the tube 25 is used to record the highfidelity audio signals from the circuit 36. The signal to the grid 13 ofthe cathode ray tube consists of a series of pulses of varying lengthsdepending upon the frequency modulation of the video information. Thebeamin the cathode ray tube 12 is, therefore turned on and off in:accordance with the successive pulses from the circuit 17.

The horizontal movement of the beam in the cathode ray tube 12 issynchronized with the video signals provided frorn the input circuit 10so that a horizontal line of the cathode ray tube 12 is initiated at thebeginning of a horizontal line of the video signals. A conventional typehorizontal sync pulse lseparator 19 may be utilized to separate thehorizontal synchronizing pulses of the video input signals from thecircuit 10. The horizontal synchronizing pulses are provided from theIseparator 19 to a phase discriminator 2t) which compares the phase ofthese pulses with the phase of pulses provided from a pulse generator30. Any difference in phase between the two sets of pulses provides foran error signal at the output of the phase discriminator 20 which isintroduced to a variable oscillator 24. The oscillator Z4 may inciude areactance tube, not shown, or other means for varying the frequency ofthe oscillator in accordance with the error signal from the phasediscriminator. The frequency of the oscillator 24, laccordingly, variesin accordance with the error signal provided thereto so as to bedirectly in step with the horizontal synchronizing pulses of the videosignals. The signal from the oscillator 24 is provided to the pulsegenerator 31B so that the pulse generator 30 is driven in step and inphase with the horizontal synchronizing pulses of the video inputsignal.

The pulses from the pulse generator 3ft are provided to a horizontalsweep circuit 31 which controls the deflection of the beam across theface of the tube 12, Vertical deiection is unnecessary because ytheimage orr the face of the cathode ray tube 12 is provided through. alens system 16 to a moving strip of recording lm 18. The film 18 may bedriven by a conventional film drive 21 to move at a relatively constantvelocity so that line `after line of the video signals are recorded onthe film due to its own motion. The speed of the film 18 determines thespacing between the successive horizontal video lines. The lines arerecorded transversely across the film strip in a direction substantiallyperpendicular to its direction of' motion.

The present invention is not restricted to photographic recordingtechniques as for exam-ple thermoplastic recording techniques may beutilized for recording the video and audio signals. When thermoplasticrecording is provided, `an electron beam in a flying spot scanner isused instead of a cathode ray tube as the transducing or recordingmeans. The specific photograph illustrative embodiment is accordinglymerely illustrative.

At the same time that the video information is being recorded line byline transversely across the lm strip 18, the audio input informationfrom the circuit 36 is also recorded on the film strip 18. The inputaudio signal from the circuit 36 is provided to an analog-to-pulseduration converter 38. The converter 38 successively samples the audiosignal and provides a succession of pulses varying in duration in,vaccordance with the instlituwus magnitudes of the audio signal. Thesampling input rate of the audio signals may be a multiple of therepetition rate of the tranverse lines across the film 18. Thehorizontal line repetition rate of the conventional video signal is15,750 lines per second. Utilizing a sampling rate system of the typedescribed herein, frequencies equal to approximately one third thesampling rate may be recorded. If the sampling rate, accordingly, is15,750 cycles per second, the upper recordable frequency of the sound isapproximately 5,250 cycles per second. For high delity recording,frequencies above these frequencies are, however, required. The samplingrate of the converter 38 is, accordingly, higher than the linerepetition rate of the video signals. Illustratively, the sampling ratemay be three times the video line repetition rate to provide forrecording sound frequencies up to about kc.

The pulse generator 30, described above, provides the pulses at arepetition rate of 15,750 pulses per second to a frequency multiplier 32as well as to the sweep circuit 31. The output of the multiplier 32 maybe a series of pulses at a repetition rate of three times 15,750 pulsesper second which is 47,250 pulses per second. These pulses from themultiplier 32 are synchronized with the input video signal because thepulse generator is synchronized therewith. The pulses from themultiplier 32 are utilized to operate a horizontal sweep circuit 34 anda blanking pulse generator 37 associated with the audio cathode ray tube25. The pulses from the multiplier 32 are also introduced to theconverter 38 for successively sampling the audio input signals. Theaudio input signals are, accordingly, sampled at a rate of 47,250 timesper second and the audio cathode ray tube 25 is operated at a linescanning rate of 47,250 lines per second.

Any conventional type of analog-to-pulse duration converter may beutilized for converting the analog audio signals to pulse durationsignals. One such converter is depicted in detail in FIGURE 1. Thesampling pulses are provided through a resistor 41 to the control gridof a triode 39 in the converter 38. A varying bias potential is providedto the control grid of the tube 39 from the audio input circuit 36, butthe magnitude of the successive pulses from the multiplier 32 isconstant. The signal at the control grid, accordingly, represents thesum of the magnitude of the sampling pulse and the instantaneousmagnitude of the audio input signal. The signal at the control grid ofthe triode 39 varies the conductivity of the triode and accordingly thepotential at its anode. The tube 39 is conductive over a path from apositive potential source through a plate resistor 43, the triode 39 anda cathode resistor 42 to ground. Between pulses from the multiplier 32,the potential at the anode of the tube 39 is determined by theinstantaneous magnitude of the audio input signal. The potential at theanode controls the discharge time of a capacitor 45 connected betweenthe anode of the triode 39 and the control grid of a triode so that thetriode 40 becomes conductive at a time determined by the instantaneousmagnitude of the audio input signal. The control grid of the triode 40is biased from a negative potential source through a resistor 47 so thatthe triode 40 remains non-conductive when only the audio signals areintroduced to the control grid of the triode 34. The lcathode of thetriode 40 is connected to the cathode resistor 42, and its anode isbiased through a resistor 48 connected to a positive potential source.Responsive to each pulse from the multiplier 32, a pulse is developed bythe converter 38 initiating at a time determined by the magnitude of theaudio input signal, The negative pulse from the converter 38 may beutilized for blanking the beam in the cathode ray tube 25.

Referring now to FIGURE 3, the successive audio lines 52 on the filmstrip 18 are each initiated and then are terminated by the converter 38at a point determined by the audio signals. The lm strip 18 may becapstan or sprocket driven at a constant speed adjacent the tubes 12 and25. The film strip 18 includes the audio recorded lines 52 and the videorecorded lines 53 shown arranged along two longitudinal or lengthwiseareas of the strip 18. Three audio recorded lines 52 are provided foreach of the video recorded lines 53. The first of each three audio lines52 may be directly in alignment with the associated video line 53.Depending upon the polarity of the pulses introduced to the tube 25, andwhether a positive or negative is made from the lm strip, one portion orthe other of the transverse line across the audio portion of the strip18 may be dark and the other light. The video portion and each line 53consists of many dark and light dashes of varying lengths depending uponthe video information.

In FIGURE 3, the longitudinal spacing of the lines 52 and 53 isexaggerated as they would be much closer together and seeming to blendone into another to an observer. For example, if the width of each trackor line 53 is .75 inch, the 262.5 lines forming a video field mayoccu-py 9%: .75-1%@ inch or have a density of approximately 466 linesper inch. The lines 53, accordingly, form a diffraction grating of lightand dark dashes of varying lengths. The appearance of the frame is gray.However, when light is provided at an angle to the hlm strip 18, asdepicted in FIGURES 4 and 5, the closely spaced successive dots in eachline 53 seem to blend together due to the interference patterns formedby the grating. As described above, the closely spaced dots representdarker portions of the scene represented by the input video signals. InFIGURES 4 and 5, light is provided from a source 163, and the lines 53are aligned in the direction of the arrow at the right of the strip 18in FIGURE 4. When viewed in this manner, interference patterns result ineffectively blending the closely spaced dots in each line 53 as acontiguous dark mass. In this manner, the portions of each line 53representing darker portions actually appears darker so that theresulting image to an observer at position 185 is essentially the sameas the original scene from which the input video signals were produced.This image may be projected and enlarged for easier viewing.

The successive frames of the video signals are recorded on the lm strip18, field by iield, with a separation between the recorded video signalsdue to the vertical blanking interval in the signals between successivefields. The video and audio information may be reproduced from the filmstrip 1S by the apparatus depicted in FIGURE 2. As shown in FIGURE 2,two flying spot scanners 65 and 32 are utilized for reproducingrespectively the video and the audio signals from the strip i8. Theflying spo-t scanner and the flying Spot scanner 82 are bothsynchronized with the movement of the film strip 1.8. The motor or filmdrive 81 drives a tachometer 84 which may include multiplying means, notshown. The output of the tachometer 84 is a series of pulses having arepetition rate or frequency which varies with the speed or" the motor81. The nominal repetition rate may be 47,250 cycles per second.

The successive pulses from the tachometer 84 are introduced as one inputto a phase discriminator 86. The other input is provided from the pulsegenerator 73 having a nominal repetition rate of 47,750 pulses persecond. The difference in phase between the pulses from the generator 73and between the dilerentiated pulses from the tachometer 84 causes thediscriminator 86 to develop an error signal in accordance therewith. Theerror signal from the discriminator 86 is introduced to a variableoscillator S7 which controls the instantaneous repetition rate of thepulse generator 73. The pulse generator 73 is, in this manner,synchronized with the movement of the film strip 13.

The pulses from the pulse generator 73 are introduced to a sweep circuit72 for controlling the horizontal line frequency of the audio scanner82. The sweep signals from the circuit 72 are provided to a deilectioncoil 83 of the audio scanner 82. The control grid 85 of the scanner 82may be grounded. The pulses fro-m the generator 73 are also introducedto a frequency divider 63 which provides pulses at a nominal repetitionrate of 15,750 pulses.

per second. The frequency division is, accordingly, by a factor of 3.The pulses from the frequency divider 63 are introduced to a horizontalsweep circuit 62 for controlling the deflection of the video scanner 65.Sweep signals from the circuit 62 are provided to a deflection coil 6dof the video scanner 65. The control grid 66 of the video scanner 65 maybe grounded. The two scanners 65 and 82 are, in this manner, operated insynchronism with the signals recorded on the film strip 18, with thescanner 82 being operated at a line scanning rate three times that ofthe scanner 65. The beamsA in the scanner 65 are blanke-tl during theretrace time so that signals are not developed at the photocells 74 and75 at such times. The signals from the film strip 18 are simultaneouslyreceived at the photocells 74 and 75 from the tWo different longitudinalareas of the film strip 18. More particularly, the signals from thevideo .lines 53 are received at the photocell 74, and the signals fromthe audio lines 52 are received at the audio photocells '75. The twophotocells 74 and 75 may be separated by a light shield 77.

The signals from the audio photocell 75 are pulse signals with eachpulse beginning at a time position indicative `of the instantaneousmagnitude of the original audio signals. The successive line scans areinitiated in the opaque parts of the successive lines 52 so that thereproduced pulses are first initiated at the beginning of the light ortransparent part of the lines 52 following the opaque parts. The pulsesfrom the generator 73 are utilized for recovering the audio signals fromthe film strip 18. The fiying spot scanner 82 scans the portion of thefilm strip 18 which includes the audio recorded lines 52 by means -of alens system Si) and a prism '79. The output of the photocell 75 is,accordingly, a series of pulses initiated at the light portions of thesuccessive audio lines 52. The signals from the photocell 75 areprovided to an amplifier and differentiating circuit 92 which provides aseries of positive pulses for resetting a ip-fiop circuit 90. Theflip-flop circuit 9th is set by a delay circuit 88 controlled by thepulse generator 73. The fiip-op circuit 90 is, accordingly, setperiodically at a substantially fixed time epoch but is reset at a timeposition varying in accordance with the audio information reproducedfrom the film strip 18. The flip-flop circuit 9th, accordingly, producesvarying duration pulses in accordance with the audio input signals.

The varying duration pulses from the flip-flop circuit 90 are providedto an integrator circuit 93 which develops a smooth varying signal whichis essentially similar to the input audio signal. The signal from theintegrator circuit 93 is amplified by an amplifier 94 and the amplifiedsignal is provided to an audio output circuit 96. At the same time thatthe audio signals are received at the circuit 96, the video signals arereceived at an output circuit 78. The circuit 73 may includedemodulating means for recovering the video signals from the frequencymodulated carrier.

The reproduction system is effective as a noise suppressing system withrespect to noise from any dirt or dust on the film strip 18. Asdescribed above, the scanner 82 initiates its trace or line scan afterthe beginning of a line 52 on the strip 18 which is upon an opaqueportion of the strip 18. The flip-dop circuit 90 is reset at a timeposition when the scanner 82 reaches the transparent portion of thestrip 18 at the end of the respective line 52. The flip-Hop circuit 90then remains reset and any dirt on the transparent portion does not setit or affect the time it is reset. Similarly, any dust or dirt on a line52 does not cause the circuit 9d to reset and, accordingly, does notaffect the reproducing accuracy or introduce a noise component.

Although this invention has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible of numerous other applications which will be apparent topersons skilled in the art.

The invention is, therefore, to be limited only as indicated by thescope of the appended claims.

What is claimed is:

1. A recording system for line scan video signals wherein a plurality ofline scans are arranged in successive frames each representing an image,including, means for frequency modulating the line-scan video signals,means coupled to the modulating means for rectangularizing the frequencymodulated signals from said modulating means to provide a series ofpulses varying in duration in accordance with the line-scan signals, amoving recording medium, means for moving said medium at a constantspeed, line scanning means positioned relative to the moving recordingmedium and coupled to said rectangularizing means for recording theseries of pulses in a succession of transverse tracks one for each lineon the moving recording medium so that images of the successive framesare recorded on the medium.

2. A recording system in accordance with claim 1, wherein the recordingmedium is a film strip, and the line scanning means is a cathode raytube for illuminating the film strip in accordance with the line scanvideo signals.

3. A recording system for line scan video signals wherein a plurality ofline scans are arranged in successive frames, each representing animage, including means for frequency modulating the line-scan videosignals, means coupled to the modulating means for rectangularizing thefrequency modulated signals from said modulating means to provide aseries of pulses varying in duration in accordance with the line-scansignals, a moving film strip, means for moving said film strip at aconstant speed, line scanning means positioned relative to the movingfilm strip and coupled to said rectangularizing means for recording theseries of pulses in a succession of transverse tracks one for each lineon the moving film strip so that images of the successive frames arerecorded on the medium, and means for providing a visible representationof the images represented in the successive frames of the line scanvideo signals, said providing means including a source of light forilluminating the recorded tracks on the film strip, said source beingpositioned to provide light along planes including the transversetracks.

4. A recording and reproducing system for a continuous signal, a movingrecording medium, means for successively sampling the continuous signalto provide a series of pulses having durations related to theinstantaneous values of said continuous signal, means coupled to saidsampling means and positioned relative to the moving recording mediumfor recording the series of pulses as a series of transverse tracksacross the moving recording medium, each track having a length relatedto the duration of the respective pulse, line scanning means positionedrelative to the moving recordingnmedium for transversely scanning themoving recording medium with each line scan initiating after thebeginning of the tracks on the recording medium, a bistable devicehaving a first and a second operating condition, means synchronized withthe bistable device for setting the device to its first condition at theinitiation of each line scan by said line scanning means, and meanscoupled to said line scanning means for setting the device to its secondcondition at the end of each recorded track whereby the device is set atits first condition for an interval related to the duration of the pulserecorded in the respective track.

5. A recording and reproducing system for a continuous signal, a movingrecording medium, means for successively sampling the continuous signalto provide a series of pulses having durations related to theinstantaneous values of said continuous signal, means coupled to saidsampling means and positioned relative to the moving recording mediumfor recording the series of pulses as a series of transverse tracksacross the moving recording medium, each track having a length relatedto the duration of the respective pulse, line scanning means positionedrelative to the moving recording medium for transversely scanning themoving recording medium with each line scan initiating after thebeginning of the tracks on the recording medium, a bistable devicehaving a first and a second operating condition, means synchronized withthe bistable device for setting the device to its first condition at theinitiation of each line scan by said line scanning means, means coupledto said line scanning means for setting the device to its secondcondition at the end of each recorded track whereby the device is set atits first condition for an interval related to the duration of the pulserecorded in the respective track, and means coupled to said device andresponsive to its operation for providing a continuous signalsubstantially the same as the input signal sampled by said samplingmeans.

6. A recording and reproducing system for a continuous signal, acontinuously moving light sensitized surface, means for successivelysampling the continuous signal to provide a series of pulses havingdurations related to the instantaneous values of said continuous signal,means coupled to said sampling means and positioned relative to themoving light sensitized surface for recording the series of pulses fromsaid sampling means as a series of opaque transverse tracks across themoving surface, each track having a length related to the duration ofthe respective pulse, line scanning means positioned relative to themoving surface for transversely scanning the moving surface with eachline scan initiating after the beginning of the tracks on the movingsurface, a bistable device having a first and a second operatingcondition, means synchronized with the bistable device for setting thedevice to its rst condition at the initiation of leach line scan by saidline scanning means, and means coupled to said line scanning means forsetting the device to its second condition at the end of each recordedtrack whereby the device is set at its rst condition for an intervalrelated to the duration of the pulse recorded in the respective track.

7. A recording system for line scan video signals Wherein a plurality ofline scans are arranged in successive frames, each representing animage, including means for frequency modulating the line-scan videosignals in a direction to provide lower frequencies for the lighterportions of the images and higher frequencies for the darker portions ofthe images, and means optically coupled to the film strip for providingvisible images substantially similar to the visible images representedin the successive -rames of the line-scan video signals.

8. In combination, a film strip having recorded thereon successive linesof frequency modulated Video signals representing successive imageswhere the modulation is in a direction of higher frequencies for darkerportions of the images, and optical means optically coupled to the filmstrip for illuminating in each image at each instant all of the recordedlines of frequency modulated signals in a direction such that the lightis provided to the film strip along planes including the recorded linesto produce optical interference patterns in the signals in the recordedlines for a blending of different positions With different intensitiesin accordance with the frequencies of the signals at such positions.

9. A method of providing a visible image of the video informationcarried by line scan video signals, including the steps of frequencymodulating the video signals on a carrier in a direction to providelower frequencies for the video signals representing lighter portions ofthe video information and higher frequencies for the video signalsrepresenting darker portions of the video information, rectangularizingthe frequency modulated carrier, recording the rectangularized carrieron a film strip as successive transverse lines made up of light and darkdots of varying lengths, and then illuminating the recorded lines on thefilm strip in a direction such that the light is provided to the filmstrip along planes including the recorded transverse lines.

it?, A method of providing a visible image of the video informationcarried by line scan video signals, including the steps of frequencymodulating the video signals on a carrier in a direction to providelower frequencies for the video signals representing lighter portions ofthe video information and higher frequencies for the video signalsrepresenting darker portions of the video information, rectangularizingthe frequency modulated carrier, recording the rectangularized carrieron a film strip as successive transverse lines made up of light and darkdots of varying lengths, then illuminating the recorded lines on thefilm strip in a direction such that the light is provided to the filmstrip along planes including the recorded transverse lines, and thenviewing the illuminated lm strip along a path perpendicular to theilluminated surface of the lm strip.

References Cited by the Examiner UNITED STATES PATENTS 2,681,382 6/1954Hilburn 17g-6.7

DAVID G. REDINBAUGH, Primary Examiner.

7. A RECORDING SYSTEM FOR LINE SCAN VIDEO SIGNALS WHEREIN A PLURALITY OFLINE SCANS ARE ARRANGED IN SUCCESSIVE FRAMES, EACH REPRESENTING ANIMAGE, INCLUDING MEANS FOR FREQUENCY MODULATING THE LINE-SCAN VIDEOSIGNALS IN A DIRECTION TO PROVIDE LOWER FREQUENCIES FOR THE LIGHTERPORTIONS OF THE IMAGES AND HIGHER FREQUENCIES FOR THE DARKER PORTIONS OFTHE IMAGES, AND MEANS OPTICALLY COUPLED TO THE FILM STRIP FOR PROVIDINGVISIBLE IMAGES SUBSTANTIALLY SIMILAR TO THE VISIBLE IMAGES REPRESENTEDIN THE SUCCESSIVE FRAMES OF THE LINE-SCAN VIDEO SIGNALS.